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Abstract Samarium niobate SmNbO4 (SNO) and tantalate SmTaO4 (STO) precursors were prepared by sol-gel method and annealing at 1000 °C. The different polymorphs, orthorhombic and monoclinic SmNbO4 or tetragonal SmTa7O19 and… Click to show full abstract
Abstract Samarium niobate SmNbO4 (SNO) and tantalate SmTaO4 (STO) precursors were prepared by sol-gel method and annealing at 1000 °C. The different polymorphs, orthorhombic and monoclinic SmNbO4 or tetragonal SmTa7O19 and monoclinic SmTaO4 were identified. Structural properties of precursors were investigated by the X-ray photoelectron spectroscopy (XPS). Core-level XPS studies of sol-gel SNO and STO were performed for the first time. The binding energy differences Δ(O Nb) = BE (O 1s) – BE (Nb 3d5/2) and Δ(O Ta) = BE (O 1s) – BE (Ta 4f7/2) were used as suitable parameter to characterize average Nb O bonding in SNO (323.1 eV) and Ta O bonding in STO (503.9 eV). The Sm 3d5/2 peak consists of strong features characteristic for Sm3+ (1083.0 eV) with (4f5) electron configuration and Sm2+ (1072 eV) with (4f6) electron configuration. The molar concentration of Sm3+ in SNO and STO was higher (21.0 and 24.7 at.%) than Sm2+ in SNO (1.0 at.%) and STO (0.3 at.%). The XPS demonstrated two valence states of Sm in precursors for application as nanophosphors for lighting and display technologies.